The objective of this work is to determine how termination of chromosome replication initiates the ensuing process of cell division. Two types of conditional cell division mutants are to be studied. Temperature-sensitive(ts)sep mutants grow and synthesize DNA normally at 42 degrees C but do not complete septum formation. The lon mutants, after temporary periods of DNA synthesis inhibition, also fail to form septa. The sep gene is located near min 2.0 in a cluster of genes related to cell division and cell membrane-cell wall function. A map of this region is to be prepared by the use of transducing phages, isolated from an unusual lysogen with lambda integrated in leu at min 1.7. These lambda sep transducing phages also will be used to identify the product of the sep gene. A complementation and genetic fine structure analysis of the lon region is proposed.